Photosynthesis

What is photosynthesis?

Photopigments absorb specific wavelengths Photosynthesis is most efficient using red and blue wavelengths

The stomata Stomata control the diffusion of CO2, H20, and O2 in and out of the leaf Plants open and close their stomata during the daytime in response to changing conditions: - light intensity - humidity - CO2 concentration The basic mechanism involves regulation of osmotic pressure

Photosynthesis on a global level…Where is it happening? 2005 NASA imaging How can we measure photosynthesis rates and what sort of events can effect this?

Exercise 1: Measuring photosynthesis  Spinach leaf disks experiment

Exercise 1: Measuring photosynthesis  Spinach leaf disks experiment Work in groups, but complete the worksheet individually NaHCO3 + H2O  NaOH + H2O + CO2 Variable one: Concentration of dissolved CO2 0 % vs. 0.2 % What variable must we maintain constant? Hypothesis and predictions? CONTROLS??

Exercise 1: Measuring photosynthesis  Spinach leaf disks experiment Work in pairs, but complete the worksheet individually NaHCO3 + H2O  NaOH + H2O + CO2 Variable one: Concentration of dissolved CO2 0 % vs. 0.2 % What variable must we maintain constant? Hypothesis and predictions? CONTROLS??  0.2 % CO2 placed in the dark. I will complete the control.

Exercise 1: Measuring photosynthesis  Spinach leaf disks experiment Complete the worksheet individually Graph your group’s results Title your graph and include units! Provide a caption for the graph Calculate the rate of photosynthesis (# of disks floating / min) Use the class data to answer the remaining questions Units

Methods 1 2 3 Run your experiment for 20 minutes! 1 2 3 Punch out 15 disks Make them sink Record the # of disks floating (every 1 min) Run your experiment for 20 minutes!

Observe the stomata Compare the top and bottom sides of spinach leaves. Is there a difference in the concentration of stomata? What is your hypothesis and what are your predictions?

Class Data Group CO2 No CO2 1 11 10 2 4 3 8 9 5 14 6 Total 49 33 Record your group’s calculated rate of photosynthesis (# of disks floating/min)

Chi-Square CO2 No Co2 Observed 49 33 Expected 41

Stomata Top Down Observed Expected

In your lab write up results Include graphs for your group’s data. (which graphs specifically?) Include the table of the class data Chi-square analysis of class data Include a brief summary of results from all your graphs and the table. You will discuss what the data mean in your Conclusion section.

Some pointers Affect vs. effect Give actual data when describing the results This study shows (not proves) Data is plural, e.g., The data were graphed. Datum is singular Diffusion and osmosis are based on the random movement of molecules. Water does not ‘want’ or ‘need’ to go…

Citation of resources MLA Format Examples of unacceptable formats: 1) Dr. Cao’s powerpoints 2) Campbell book 3) Photosynthesis website